This invention relates to a gene showing specific expression in monocotyledon flower organs and its promoter sequence. This invention further relates to a chitinase acting as a defensive mechanism against pathogenic bacteria and a chitinase gene.
There have been reported some cases of the isolation of genes which are expressed specifically in flower organ, for example, anther-specific genes and pistil-specific ones. However, only a few genes specific to another have been reported as genes which are isolated from monocotyledons and for which the promoter sequences have been clarified.
These reports are exemplified by JP (Kohyo) HEI 6-504910, Tsuchiya et al. Plant Mol. Biol. 26, 1737-1746, 1994, etc. in which the nucleotide sequences of rice anther-specific genes, their expression profiles, etc. are indicated.
Promoters exhibiting expression specifically in flower organ are required in order to artificially improve the morphology of plant flower organs, in particular germ organs, or physiological phenomena or to analyze functions of various genes in flower organs. In monocotyledons which represent major cereals, however, few genes expressed exclusively in flower organs have been isolated hitherto. In particular, there has been reported no promoter sequence showing predominant expression in pistil which is the female germ organ or lodicule which regulates flowering.
Although chitinase (EC 3.2.1.14), which seemingly acts as a defensive mechanism against pathogenic bacteria and fungi, can be cited as an example of genes expressed in flower organ, most of the chitinases of plant origin reported so far are constitutively expressed not only in flower organs but also in roots (see, for example, Neale et al. The Plant Cell, 2, 673-684, 1990). Exceptionally, chitinases such as potato SK2 (Wemmer et al. Planta 194, 264-273, 1994) and tomato Chi2;1 (Harikrishna et al. Plant Molecular Biology, 30, 899-911, 1996) show style-specific expression.
On the other hand, there have been isolated some chitinases of monocotyledons. For example, Zhu ant Lamb (Mol. Gen. Genet., 226, 289-2961991) isolated a chitinase called RCH10 from rice and reported that the gene of this enzyme was constitutively expressed in root under aseptic conditions. Further, Zhu et al. (BIO/TECHNOLOGY, 12, 807-812, 1994) constructed tobacco with enhanced tolerance to pathogenic bacteria by using the above-mentioned gene together with an alfalfa glucanase gene.
There has been no report in monocotyledons, however, about a chitinase which is not expressed at a detectable level in root, being expressed exclusively in flower organs.
An object of the present invention is to provide a novel flower organ-specific promoter sequence enabling genetic manipulations of pistil or lodicule which were impossible in the prior art particularly in monocotyledons.
Another object of the present invention is to provide a novel chitinase which makes it possible to impart to plants a general resistance against pathogenic bacteria and fungi containing chitin.